I assembled this deck from wikipedia’s mnemonic major system page:
The major system … is a mnemonic technique used to aid in memorizing numbers.
The system works by converting numbers into consonant sounds, then into words by adding vowels. The system works on the principle that images can be remembered more easily than numbers.
An example, from wikipeida:
Each numeral maps to a set of similar sounds with similar mouth and tongue positions. For most people it would be easier to remember 3.1415927 (an approximation of the mathematical constant pi) as:
meteor (314, /m/-/t/-/r/)
tail (15, /t/-/l/)
pink (927, /p/-/N/-/k/, and taking /N/ to be 2)